1. Field of the Invention
The present invention relates to production equipment used in manufacturing a semiconductor device, and more particularly to a slurry supply unit for a CMP (Chemical Mechanical Polishing) apparatus for uniformly supplying the slurry containing a polishing agent to the CMP apparatus.
2. Description of the Related Art
As semiconductor devices are highly integrated, the wire structures tend to have multi-layers and level differences between stacked unit cells increase. The level differences can generate inferiority of the devices, and various methods have been suggested to reduce the level differences.
A CMP apparatus is production equipment used in a planarization process of a semiconductor device that chemically and physically polishes a surface of a semiconductor wafer using slurry including a mixture of a polishing agent and DI-water and a polishing pad rotating together with the slurry.
On the other hand, in the planarization process using the CMP apparatus, a plurality of CMP units are generally connected to one slurry supply unit to reduce the manufacturing cost.
FIG. 1 shows a preferred embodiment of CMP equipment including a conventional slurry supply unit.
As shown in FIG. 1, the conventional CMP equipment connects a plurality of CMP units 30a to 30n to one slurry supply tank 10. A slurry circulation line 20 is connected to a slurry supply tank 10 and slurry is supplied to the CMP units 30a to 30n through the slurry circulation line 20.
The slurry is circulated, for example, in direction A in the slurry circulation line 20 through a main pump 12 installed in the slurry supply tank 10 and is supplied to the CMP units 30a to 30n through the slurry distribution lines 22a to 22n that branch out from the slurry circulation line 20. The slurry distribution lines 22a to 22n are connected to the CMP units in a one to one relationship. The slurry supplied to the CMP unit through the slurry distribution lines 22a to 22n is injected onto a rotational table of a CMP unit through the corresponding slurry injection pipe 32.
Further, in the CMP units 30a to 30n, a wafer 38 is fixed to a carrier 36 and is generally located on the rotational table 34 to which a polishing pad of a resilient material is attached. Then, a uniform downward force is applied through the carrier 36 and one surface of the wafer 38 makes contact with the polishing pad. Thus, if the rotational table 34 is rotated at a predetermined speed, the wafer 38 is rotated at a predetermined speed together with the carrier 36. A predetermined amount of slurry is distributed on the rotational table 34 or the polishing pad through a slurry injection opening 32. Therefore, the polishing operation of the slurry and the rotation of the rotational table 34 and the wafer 38 are combined with each other to polish a surface of the wafer 38.
The above-mentioned central supply method supplying slurry to a plurality of CMP units with one slurry supply unit is advantageous in the aspect of cost reduction. However, in the central supply method, the flow amount or rate of the slurry branched to the CMP units may become different according to the operation degree of the CMP units. Namely, the flow amount of the slurry can be different in each CMP unit 30a-30n. In this case, since the amount of the slurry reacting with a surface of a wafer may differ from unit to unit, the polishing amount may become non-uniform, thereby exerting undesired variations in the polished devices and an adverse influence on the CMP characteristics.